Slide valve



Oct. 19, 1954 2, EDMUNDSON 2,692,115

SLIDE VALVE Filed April 27, 1951 8 1 S Li DEVALVE.

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Zerah F Fa'mundson A T TOENEY Patented Oct. 19, 1954 SLIDE VALVE Zerah F. Edmundson, McKeesport, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application April 27, 1951, Serial No. 223,31l'

3 Claims.

This invention relates to slide valves of the type employed in the triple valve devices of railway braking equipment, and more particularly to an improvement in such slide valves for preventing the formation of a square shoulder in the slide valve seat at end of valve travel.

When the travel of a slide valve is so limited that the slide valve cannot overtravel its seat in any degree, the resultant longitudinal groove that is gradually formed in the valve seat as a result of the reciprocating sliding movement of the valve will terminate in a transverse shoulder at the extreme limit of valve movement.

Such a transverse shoulder when approached by the usual blunt square end of the slide valve will act as a backstop for any of the small metal wear particles swept over the seat by the valve. Such particles, under repetitious compressive influence of shoulder and valve will accumulate to form an ever lengthening stop shoulder which gradually shortens the travel of the valve and so alters its function as in time will interfere with its operation.

In view of the foregoing, it is a prime object of the invention to provide an improved slide valve which will be free of the abovedescribed trouble.

Other objects and advantages of the invention will become obvious from the following detailed description taken in connection with the accompanyin drawing in which:

Figs. 1 and 2 are two elevation views of a portion of a slide valve embodying the invention and its seat, before and after prolonged wear, respectively.

Description Referring to Fig. 1 in the drawing, an end portion of a slide valve i is shown seated on a slide valve seat 2 in slidable engagement therewith. The slide valve 6 may contain the usual port or passage 2a, for example, and the seat 2 may contain the usual port or passage it, for example; said ports or passages 2a and 2b being so adapted and arranged that Sliding movement of valve l on seat 2 into and out of the position in which it is shown in the drawing will carry port or passage 2a into and out of registry with port or passage 21).

According to the invention, whichever end or ends of a slide valve may travel repetitiously to a position on the slide valve seat, such as the position of the valve on seat 2 indicated by a dotand-dash line la, and defined by such as contact of a stop surface I 6 with a fixed stop 3, is provided with a slot 4 to form an inwardly and upwardly extending surface 5 intersecting the original lower or seating face 6 of the slide valve l which slidably engages the original upper seating surface i of the valve seat.

As the slide valve l is reciprocably moved into and out of the position in which it is shown in Figs. 1 and 2, a groove 8 is worn in the valve seat 2 which will define a recessed seatin surface 1 below the original seating surface 1 while the slide valve i will wear in thickness to a new face 6 in slidable engagement with recessed seating surface I.

According to the invention, by virtue of the tapered surface 5 at the end of the slide valve, any wear particles which might otherwise tend to accumulate on the valve seat will be scraped on by the relatively sharp end defined by such surface 5. Even more important, however, as the valve wears in thickness by some such amount as b, the tapered end of the lower seat-engaging face of the valve 1 will recede further away from stop surface iii by some such amount as 0, so that, during continued reciprocating movement of valve l on seat 2, instead of wearin a blunt substantially square transverse shoulder in the seat at the respective end of the groove 8, said valve, by virtue of its continually shortening tapered end, will form a gently tapered transverse surface 9 in the seat at the respective end of the groove 8 which surface 9 will allow for facile displacement of wear particles out of said groove 8 by scooping action during valve movement in the direction of stop 3; thereby precluding trapping of foreign matter in said groove which would interfere with such movement.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A slide valve of the type having a flat seating surface for slidable engagement with a flat slide valve seat and having means cooperable with a port in said seat to control communication through said port, said slide valve being characterized by a sloping surface thereon intersecting one end of said flat seating surface at such an angle that as the thickness of the valve reduces due to wear of its said seating surface the length of said seating surface automatically reduces to prevent the wearing of a square shoulder in the valve seat with return of said valve repetitiously to a particular stop position on the seat.

2. In combination, a flat slide valve seat, a slide valve having a flat seating surface in slidable engagement with said seat, said slide valve and said slide valve seat havin cooperating means to 3 control flow of fluid, stop means operable to determine limit position of travel of said slide valve on said seat, said slide valve being characterized by a sloping surface thereon intersecting one end of said seating surface at such an angle that as the thickness of the valve reduces due to wear of its seating surface the length of said seating surface automatically reduces to prevent the wearin of a square shoulder in the valve seat as the valve is returned repetitiously to its limit position as determined by said stop means.

3. In combination, a fiat slide valve seat having a fluid pressure port therein, a fixed stop element, and a slide valve having a flat seating surface in slidable engagement with said valve seat, having means cooperable with said port to control communication therethrough according to position of said slide valve on said seat, having a stop surface extending at right angles to said element to define a limit position of travel of said valve with respect to said port, and being characterized by a sloping surface thereon orig-inating at the end of said seating surface nearest said stop element and extending transversely of said valve in the direction of the opposite end of said seating surface so that as the thickness of said valve reduces due to wear of said seating surface the length of said seating surface will automatically reduce to avoid the wearing of a shoulder in said seat capable of entrapping particles which would prevent the full movement of said valve to its limit position.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,117,894 Orbin Nov. 17, 1914 1,470,460 Lorraine Oct. 9, 1923 2,000,853 Lange May 7, 1935 

